add test coverage for `bin/setup`.

Make sure this script keeps working and has consistent output.

railties/test/application/bin_setup_test.rb

+require 'isolation/abstract_unit'
+
+module ApplicationTests
+  class BinSetupTest < ActiveSupport::TestCase
+    include ActiveSupport::Testing::Isolation
+
+    def setup
+      build_app
+    end
+
+    def teardown
+      teardown_app
+    end
+
+    def test_bin_setup
+      Dir.chdir(app_path) do
+        app_file 'db/schema.rb', <<-RUBY
+          ActiveRecord::Schema.define(version: 20140423102712) do
+            create_table(:articles) {}
+          end
+        RUBY
+
+        list_tables = lambda { `bin/rails runner 'p ActiveRecord::Base.connection.tables'`.strip }
+        File.write("log/my.log", "zomg!")
+
+        assert_equal '[]', list_tables.call
+        assert_equal 5, File.size("log/my.log")
+        assert_not File.exist?("tmp/restart.txt")
+        `bin/setup 2>&1`
+        assert_equal 0, File.size("log/my.log")
+        assert_equal '["articles", "schema_migrations"]', list_tables.call
+        assert File.exist?("tmp/restart.txt")
+      end
+    end
+
+    def test_bin_setup_output
+      Dir.chdir(app_path) do
+        app_file 'db/schema.rb', ""
+
+        output = `bin/setup 2>&1`
+        assert_equal(<<-OUTPUT, output)
+== Installing dependencies ==
+The Gemfile's dependencies are satisfied
+
+== Preparing database ==
+
+== Removing old logs and tempfiles ==
+
+== Restarting application server ==
+        OUTPUT
+      end
+    end
+  end
+end